Reason for Concern:
1) Affects ‘Boysenberry’, ‘Loganberry’ and ‘Marionberry’ blackberries, and some newer cultivars.
2) Results in quality and yield loss.
3) Fruit often will not make IQF grade and is sold at lower value for juice, jam or puree.

Identification/Symptoms:
Most commercially recommended varieties do not show any leaf symptoms. Leaf tissue lab testing is the only way to confirm presence of RBDV. Crumbly fruit is the most common symptom, but other factors can cause crumbly fruit. Infected plants are neither bushy nor dwarfed, but stunting and shorter canes occur in some varieties. Leafs of some varieties also turn yellow in spring. In ‘Marion’, bright yellowing on primocane leaves and leaf bleaching on fruiting canes occurs in late summer.

Disease Cycle:
A seed and pollen-born virus that spreads during bloom, honeybees move the infected pollen from plant to plant. A pollinated blackberry flower infects the embryo and the mother plant. The exact mechanism by which RBDV infects the seed and mother plant is unknown. Temperature, humidity levels, insect vectors and spread from native vegetation can affect transmission. Studies have already shown that native Rubus species such as thimbleberry (R. parviflorus) can be naturally infected with RBDV.

• Oregon State University Online Plant Disease Manual

• Watch for leaf symptoms (yellowing along veins and leaf peripherals) and crumbly fruit.
• Symptoms on blackberry are not diagnostic as crumbly fruit can be caused by a variety of different stresses such as root rot, poor nutrition or poor pollination.
• Mark suspect bushes and have leaf samples tested at a laboratory.

• There is no cure for this disease. Remove infected plants to prevent bees from vectoring the disease through pollen transfer.

For information about chemical controls, check with our Pesticide Guide.